Objectives Prescription opioid overdoses are a leading cause of death in the United States. Emergency departments (EDs) are potentially high-risk environments for doctor shopping and diversion. The hypothesis was that opioid prescribing rates from the ED have increased over time. Methods The authors analyzed data on ED discharges from the 2006 through 2010 NHAMCS, a probability sample of all U.S. EDs. The outcome was documentation of an opioid prescription on discharge. The primary independent predictor was time. Covariates included severity of pain, a pain-related discharge diagnosis, age, sex, race, payer, hospital ownership, and geographic location of hospital. Up to three discharge diagnoses were available in NHAMCS to identify "pain-related" (e.g., back pain, fracture, dental/jaw pain, nephrolithiasis) ED visits. Multivariate logistic regression was performed to assess the independent associations between opioid prescribing and predictors. All analyses incorporated NHAMCS survey weights, and all results are presented as national estimates. Results Opioids were prescribed for 18.7% (95% confidence interval = 17.7% to 19.7%) of all ED discharges, representing 18.8 million prescriptions per year. There were no significant temporal trends in opioid prescribing overall (adjusted p = 0.93). Pain-related discharge diagnoses that received the top three highest proportion of opioids prescriptions included nephrolithiasis (62.1%), neck pain (51.6%), and dental/jaw pain (49.7%). A pain-related discharge diagnosis, non-Hispanic white race, older age, male sex, uninsured status, and Western region were positively associated with opioid prescribing (p <0.05). Conclusions No temporal trend toward increased prescribing from 2006 to 2012 was found. These results suggest that problems with opioid overprescribing are multifactorial and not solely rooted in the ED.